Method of forming hollow vanes and blades for gas turbines



P 11, 1962 A. o. SHERMAN 3,052,961

METHOD OF FORMING HOLLOW VANES AND BLADES FOR GAS TURBINES Filed Feb. 4, 1960 2 Sheets-Sheet 1 A TIDE/V576 Sept. 11, 1962 A. o. SHERMAN 3,052,961

METHOD OF FORMING HOLLOW VANES AND BLADES FOR GAS TURBINES Filed Feb. 4, 1960 2 Sheets-Sheet 2 Unite tates 3 052,961 NIETHUD F FQRmIG HOLLGW VANlS AND BLADES FOR GAS TURBlNES Alden 0. Sherman, Weston Road, Weston, (Donn. Filed Feb. 4, 1960, Ser. No. 6,7 46 1 Claim. (Cl. 29156.8)

As conducive to an understanding of the invention, it is noted that the use of hollow vanes is generally desired for jet engine turbines, for example, because of their light weight and the ability to pass cooling gas therethrough. For such a vane to function efliciently, it must have desired aerodynamic characteristics which, among other things, is determined by the cross section or air foil of the vane, its twist, width, taper and thickness.

Where, to form such hollow vane with the desired cross section or air foil, a length of tubing is utilized, with an anvil inside the bore thereof and a complementary die, no twist can be formed in the vane, for the internal anvil would be clamped and could not be removed. In addition, the width of the vane would be constant unless the tubing was tapered, which is relatively diflicult to form. Pu:- thermore, where tubing is used, the trailing edge of the vane would comprise two thicknesses of metal, which would detract from the desired air flow characteristics, and where such trailing edge is compressed to reduce the thickness thereof the reverse bend would be weakened with likelihood of breakdown.

Where a blank of sheet metal preformed to the desired shape is reversely bent into U shape and the trailing edges welded and trimmed and the closed unit then filled with wax which is hardened to permit final forming of the vane and the wax is then removed, there will be a spring-back of the metal, which must be accounted for in order that successive vanes formed as above described will be iden tical and of desired aerodynamic characteristics. This is difiicult and time-consuming and not practical with small vanes, due to the difiiculty of holding tolerances.

It is accordingly among the objects of the invention to provide a method for forming hollow vanes for jet engines or the like, which method requires a minimum number of operations that may readily be performed at relatively low cost and repeated to provide substantially identical hollow vanes, each having a cross section or air foil and a twist for desired aerodynamic characteristics.

According to the invention, these objects are accomplished by the arrangement and combination of elements hereinafter described and more particularly recited in the claim.

In the accompanying drawings in which is shown one of various possible embodiments of the several features of the invention,

FIG. 1 is a perspective view of a vane formed by the method herein described,

FIG. 2 is a perspective View of an insert used as part of the method,

FIG. 3 is a plan view of a vane blank, and

FIGS. 4 to 7 inclusive are successive stages in the formation of the vane.

Referring now to the drawings, a ductile metal blank- 11 of the desired shape and size is reversely bent as at 12 into substantially U-shape by means of a suitable die to form the contour of the leading edge 13 of the vane 14.

Thereupon, a section of strip 15 which is shown cross hatched in conventional manner to indicate that it is of metal in the embodiment shown, having a cross section corresponding to the desired air foil of the finished vane, and of shape corresponding to the desired inside contour of the finished vane, is inserted into the semi-formed vane 12 above described as shown in FIG. 5.

The semi-formed vane with the insert 15 is then placed add into a die 16 (FIG. 6) to coin or squeeze the trailing edge 17 and trim off excess material as at 13.

The semi-formed vane with its insert is then placed into a final forming member of the type shown in FIG. 7. The forming member has a base 19 in which is positioned a die 21 which has the desired twist conformed therein. The semi-formed vane 12, with the insert 15 therein, is positioned on the die 21 and subjected to the force exerted by a punch 22..

As shown, this punch 22 has a rubber pad 23 in the underface thereof, which presses against the vane to bend the latter into conformity with the die 21.

By the use of the rubber punch 22, even if there are variations in the insert 15 due to manufacturing tolerances and hence irregularities in the surface of such insert, since the rubber 23 will flow, it will exert an equal pressure on the vane so that there will be no hard spots which cause stress to the metal and possibly variations in spring-back so that successive vanes would differ one from the other.

The vane thus far formed has the desired air foil, twist, width and thickness. To complete the vanes, the insert 15 is removed from the interior thereof, which can readily be accomplished as the trailing edge 17 of the vane is open, and thereupon such trailing edge 17 is brazed or welded to complete the vane.

If it is desired to form a tapered vane, this can be accomplished by forming the insert 15 to the exact size and shape of the inside of the wane and using such insert in association with a blank 11 having the desired taper.

With the relatively simple method above described, hollow vanes may readily be formed at relatively low cost and with assurance that successive vanes made by such method will be substantially identical.

As many changes could be made in the above method and many apparently widely different embodiments of this invention could be made without departing from the scope of the claim, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

The method of forming hollow vanes, which comprises bending a blank of ductile metal of predetermined contour and size into substantially U-shape to define the leading edge of such vane, positioning a rigid metal insert having the desired cross section or air foil inside said bent blank, pressing the open edges together to define the trailing edge of the vane and trimming ofi excess material beyond the desired width of the finished vane and thereupon placing the bent blank with its contained insert on a die having the desired twist, positioning a resilient pad contained in a cavity of fixed volume over the bent blank and applying pressure to bring the bent blank and the pad into engagement to conform the blank and the insert to the twist of the die.

References Cited in the file of this patent UNITED STATES PATENTS 1,916,027 Weinberg June 27, 1933 2,377,664 Berger June 5, 1945 2,449,428 Timmons Sept. 14, 1948 2,522,683 Lurcott Sept. 19, 1950 2,799,918 Goldthwaite et al July 23, 1957 FOREIGN PATENTS 770,908 France Sept. 24, 1934 1,050,891 France Jan. 12, 1954 757,502 Great Britain Sept. 19, 1956 

